It is known that biopsy is an operation allowing a surgeon to remove a certain amount of tissue from a living body for the purpose of examining it in a laboratory.
In order to carry out this operation it is necessary to have instruments adapted to penetrate the organ to be examined while causing the minimum traumatism to patients by virtue of a very rapid action. Furthermore, these instruments must be capable of removing a rather important amount of tissue so that all necessary analyses can be performed thereon.
For the purpose needle-like instruments usually called biopsy needles are commonly used. Among them a very efficient needle is the so-called Menghini needle, by the name of its inventor. This instrument substantially consists of a syringe the outer cylindrical body of which is connected at one end to a biopsy cannula or hollow needle. Inside said outer cylindrical body is slidably engaged a piston carrying at one end a needle-like stylet adapted to slidably engage in the cannula of the outer cylindrical body. Said stylet consists of a metal thread-like element provided with a longitudinal milling adapted to allow the suction to be transmitted inside the biopsy chamber when the piston, which defines a suction chamber together with the outer cylindrical body, is suitably drawn in the cylindrical body itself.
In this kind of needle, while the outer biopsy cannula is suitably sharpened for cutting, the stylet has a penetrating conical point normally projecting from the cannula.
The above described instrument is used, as already said, for dissecting and drawing a certain amount of tissue from organs to be examined. Said organs may be for example the liver, the prostate or even an unknown mass such as that of a tumor, in order to determine the type of neoplasm concerned and consequently the exact therapy to be performed.
Supposing that it is necessary to reach the liver in order to remove a certain amount of tissue, the instrument is used in the following manner. The syringe is first maintained with the piston inserted at the bottom of the outer cylindrical body. In this condition, with the stylet point projecting from the cannula, the needle is caused to penetrate under the dermis; it crosses the subcutaneous fats and comes close to the liver without removing any tissue. At this point the surgeon puts the syringe under suction so that the stylet disappears inside the cannula up to a stop member disposed on the syringe for the purpose of avoiding the cylindrical body-piston assembly being maintained pulled by the surgeon itself.
Now, by a quick motion, the biopsy cannula is caused to penetrate into the liver; so it dissects the tissue and is filled with the same, assisted by the vacuum previously produced in the suction chamber. Then it is necessary to withdraw the cannula from the body together with the dissected tissue which is called biopsy fragment.
Always by effect of the vacuum created inside the syringe, the fragment is retained inside the cannula being withdrawn, until it is torn at its bottom and remains therefore in the cannula itself which is still under vacuum. Afterwards the piston must be pushed inside the syringe again in order to eliminate the vacuum and to cause the stylet to eject the removed fragment.
However the above described instrument, notwithstanding its undoubted technical and operative advantages, has some drawbacks.
A first drawback resides in that, when it has to deal with rather compact tissues such as those of a liver suffering from cirrhosis or with a very fibrous tumor or a rather hard prostate, it does not succeed in tearing the fragment off owing to the insufficient vacuum determined inside the syringe. Therefore the use of this instrument appears rather limited above all where the oncologic field is concerned.
In fact it has been noticed that when the needle comes close to the organ to be submitted to biopsy and the syringe is disposed under vacuum before penetrating the organ to be examined, blood and other physiological liquids are drawn inside the syringe and when afterwards the organ is penetrated by the cannula, the latter further fills up with blood and tissue so that the vacuum inside the syringe drops. In other words, the maximum vacuum state occurs at the beginning of the biopsy cannula penetration into the organ to be examined, while the maximum vacuum should be desirable at the moment of the cannula extraction from the organ due to the fact that a high vacuum state facilitates the fragment tearing off.
A further drawback of this type of instrument resides in that the penetration into the organ, for example the liver, requires as rapid a movement as possible because said penetration takes place between two ribs and therefore the patient might react by a sudden movement which would cause the needle to move inside the liver giving rise to well imaginable damages.
Furthermore, under that circumstance, a further drawback is given by the fact that the surgeon does not succeed in controlling the penetration with the risk of passing the organ being examined right through. The latter drawback is mainly due to the fact that it is practically impossible to adjust the needle penetration.
It should also be understood that should an unknown mass be examined, which could be a tumor as big as a walnut, the through penetration of that mass would be rather easy which could cause the insemination of parts of that tumor to not yet infected organs.
Beside these primary disadvantages, it is also possible to detect further disadvantages of less consequence such as for example the fact that the syringe must be operated with both hands, whilst it should be desirable to carry out the operation using only one hand.
Finally, a further drawback is represented by the shape of the stylet which, having a conical point, causes, at its penetration into the organ, tearings that heal up with more difficulty with respect to the clear cuts produced by the cutting point of a stylet consisting of a cannula provided with a three-side sharpening.